1. Field of the Invention
This invention relates to a method for controlling a fan of an electronic photo device. More specifically, the present invention relates to a method for controlling the operation of the fan in the electronic photo device to keep the temperature in the device as a suitable level to the characteristics of print papers and thereby provide an enhanced print quality.
2. Description of the Related Art
Generally, an electronic photo device such as a copying machine and a printer includes a pickup roller, a charging roller, an organic photoconductive (OPC) drum, a transferring roller, a developing roller, a supplying roller, a fixing unit and an exposing device, a cleaning blade, a fan for keeping the temperature in the electronic photo device from increasing, an output sensor for sensing the output of a printed paper, and a printer controller for controlling the above-described components and performing data printing operation. By means of the components, the electronic photo device prints a predetermined image data on a print paper.
The charging roller, the developing roller, the transferring roller and the supplying roller are provided with a charging voltage of -1.4 kV, a developing voltage of -300 V, a transferring voltage of +2.0 kV, and a supplying voltage of -500 V, respectively.
Now, the printing process by the electronic photo device will be described hereinafter. First, the charging roller is charged by the charging voltage with a high pressure and rotated to evenly charge a photosensitive body formed on the outer periphery of the OPC drum. At this time, a light emitted from the exposing device forms an electrostatic latent image on the outer periphery of the charged OPC drum. Then, a potential difference occurs between the supplying roller supplied with a high pressure supplying voltage and the developing roller supplied with a lower voltage than the supplying roller.
Accordingly, negative charges move from the supplying roller to the developing roller. In this manner, toner is moved from the supplying roller to the developing roller. The toner is then coated on the electrostatic latent image formed on the outer periphery of the OPC drum so that the electrostatic latent image is changed into a visible image. The transferring roller with a high pressure transfers the visible image formed on the OPC drum with the toner to a transferred paper. The transferred visible image is fixed to the paper by heat and pressure of the fixing unit. In this manner, the printing process is completed.
On the other hand, the electronic photo device adopts at least a single fan to cool the heat used in fixing the toner to the print paper and keep the fixing temperature as a lower level than a predetermined temperature.
However, the electronic photo device including the fan suffers from several problems.
In the event that a great heat is initially supplied to the print paper with much toner coated thereon, there is a phenomenon that the paper is ironed by the heat and, resultantly, the paper may be wrinkled.
Moreover, in the case of an overhead projector (OHP) film, humidity and dyestuff of the overhead projector film is vaporized by the great heat. As a result, the fixed state of the toner is deteriorated and the printed image may be transformed.
Examples from the conventional art involving operation of electrophotographic devices are seen in the following U.S. Patents.
U.S. Pat. No. 5,379,999, to Barzideh et al, entitled Sheet Media Handling Apparatus, describes an electrophotographic device in which the sheet media is controlled by air from a fan.
U.S. Pat. No. 5,457,516, to Kim, entitled Energy Saving Image-Forming Apparatus And Control Method Therefor, describes a printer apparatus including a ventilation fan for cooling the internal portions of the printer. The method includes turning off the power to the fan when the apparatus fails to receive an input within a predetermined time period.
U.S. Pat. No. 5,666,187, to Kim, entitled Method And Apparatus For Controlling The Driving Of An Ozone Emission Fan In An Image Forming Apparatus, describes driving the ozone emission fan when an external printing command is received and stopping the ozone emission fan after the printing operation.
U.S. Pat. No. 5,956,554, to Yanashima et al, entitled Sheet Driving Prevention Device, describes a printer with fans in the vicinity of the fixing device to blow air onto a continuous form when printing is stopped, to prevent heating of the continuous form.
Based on my reading of the art, then, I have decided that what is needed is an improved method for operating an electrophotographic device which prevents damage to the image on an overhead projector film.